Processing of endosperm splits



United States Patent James L. Keen New Brighton, Minnesota 709,946

March 4, 1968 Dec. 1, 1970 General Mills, Inc.,

a corporation of Delaware Inventor Appl. No. Filed Patented AssigneePROCESSING OF ENDOSPERM SPLITS B02 c 4/00; B23b 1/30 Field ofSearch146/221.8, 221.9, 221.7; 241/6, 9, 12; 99/98 References Cited UNlTEDSTATES PATENTS 1,136,501 4/1915 Andrews 241/6 2,131,674 9/1938Salomonetal. 24l/12X 3,132,681 5/1964 Keenetal 146/2218 3,318,536 5/1967Graumann 241/6 FOREIGN PATENTS 539,066 4/1957 Canada 241/12 PrimaryExaminerW. Graydon Abercrombie Attorneys-Anth0ny A. Juettner, William C.Babcock and I Jermoe .l. Jenko ABSTRACT: An improved process of treatingseeds containing galactomannan polysaccharides wherein endosperm splitsPROCESSING OF ENDOSPERM SPLITS The present invention relates to aprocess of treating seeds containing galactomannan polysaccharides insuch a manner so as to produce a mucilaginous material which is rapidlydispersible in water to produce aqueous sols of unexpected highviscosity. In particular this invention relates to a process of flakingor squeezing endosperm sections of galactomannan polysaccharidecontaining seeds.

This invention involves the use of seeds from the plant familyLeguminosae such as tara, guar, locust bean, honey locust, palo verde,and other seeds which contain neutral polysaccharides of high molecularweight with numerous short branches. These polysaccharide gums have theability to swell greatly in water to produce viscous sols. Locust beanand guar seeds are especially valuable for their polysaccharide content.These seeds or beans have a nominal diameter of approximatelythree-sixteenths of an inch for guar seeds and approximatelyfive-sixteenths of an inch for locust seeds. The structure of the bean,in both cases, is such that it consists of two hemispheric endospermpieces, one on either side of two adjacent disk-shaped germ pieces withthe whole covered by a layer of hull material. The hull is thin andhard; the endosperm is very hard, and the germ is soft and pliable. Whenthe beans are submitted to an impact, the endosperm sections split,generally in half. The embryo or germ may likewise split remainingattached to endosperm sections. The germ may be detached and ground.Such endosperm half sections are hereinafter referred to as splits. Theendosperm splits are extremely tough and have a normal moisture contentof lO-l 2 percent. It is normally desirable to remove the hull from theouter covering of the splits. A suitable method of splitting anddehulling the guar beans to get at the endosperm splits is disclosed inUS. Pat. No. 3,132,68l. Preferably the beans are split and sifted toseparate splits and germ. The splits are heated with steam to loosen thehull and stabilize the endosperm. The splits are cooled and thensubjected to controlled impact sufficient to loosen the hull. The hullbecomes broken and ground as a result of impact and abrasion with otherparticles during milling. Suitable impact is provided by a hammer mill.

The product from the dehulling mill is sifted in conventional equipmentfitted with screens of proper size to pass the broken and ground hullparticles while retaining the germ-free, dehulled, coarser sizedendosperm product. Any germ fragments which might still be clinging tothe endosperm after the splitting step are dislodged and separatedduring the dehulling step. The hull fraction is recovered as abyproduct. The endosperm product is ground to guar gum for commercialusage.

Optionally, the product from the dehulling mill is die divided in thesifter into three fractions, namely, the hull byproduct fraction whichmay also contain some fine bean meal, the large endosperm splits, and anintermediate fraction composed of middling splits and meal. Thisintermediate fraction is then subjected to a gravity table to recoverthe smaller and broken endosperm splits which are combined with thelarge endosperm splits to make up the endosperm product.

it has now been found that the mucilaginous material when processed asdisclosed herein is unexpectedly, rapidly, water dispersible andproduces aqueous sols of unexpected fast solution or rapid hydration andhigh viscosities. in order to obtain these results it has been foundthat the splits must be reduced to a thickness ofless than 25 microns.

This invention in its broadest sense encompasses the processing ofsplits wherein the splits are reduced to a thickness of less than 25microns, desirably less than 20 microns, and preferably less thanmicrons, at a tempered moisture content of 30-70 percent, desirably43-62 percent and preferably 48-56 percent. When processing the splitsas disclosed herein, each split undergoes a size expansion, i.e. thesurface area each split covers is expanded approximately 100- l50 timesor more. It has been calculated that an average split particle covers anarea of approximately 0.07 cm. and after processing is expanded to coveran area of 7.010.5 cm. By submitting the splits to such processing, i.e.a thickness of less than 25 microns, the cells and cell walls of thesplits apparently rupture and are squeezed empty so that thegalactomannan gum is free to rapidly dissolve and rapidly hydrate and tocause the high viscosities in aqueous sols.

When practicing a preferred embodiment of this invention, splits aretempered until the moisture content is preferably 43- 62 percent. Thetempered splits are then ruptured or flaked, preferably between tworolls so that the tempered split is reduced to a flake thickness of lessthan 25 microns causing the gum to diffuse or be squeezed from the cell.

When processing splits, it is preferable to temper the splits bytreating with water to increase the moisture content. Such a treatmentsoftens the splits. When tempering, the splits usually expand in size. Aguar bean split usually expands approximately percent in volume at 50percent moisture content. The tempering step is a process of moistureequilibration within the individual split; the equalizing of moisturefrom the periphery to the heart or center of the individual split. Sinceit involves moisture transfer through individual cells, and cell wallsfrom the periphery to the heart or center of the split, temperingrequires time. Generally 2030 minutes is suffi cient at ambienttemperature to allow moisture equilibration but times up to 1 hour havebeen satisfactorily used. When processing the splits after dehulling andtempering to produce a flake of less than 25-micron thickness, it ispreferable to pass the tempered split between flaking rolls. It has beendetermined that rolls set with a feed rate such that flake thickness inthe nip is l0-l2 microns will give a product with a 2-minute viscosityapproaching 6,000 centipoises. Rolls set with a feed rate such thatflake thickness in the nip is 40 microns and above will produceconsiderably lower 2-minute viscosities.

Since, the split is reduced in thickness to less than 25 micronsandexpanded in area to approximately l00l50 times its original area,many physical processing properties may significantly influence thefinal flake size. if flaking rolls are used, the physicalcharacteristics of the rolls maybe im portant. Roll pressure, rolldiameter, uniformity of roll diameter, nature of the surface of theroll, roll r.p.m., roll temperature, feed rate, nip width, and positionof the flaker knives may be contributing variables. For instance whenoperating the laboratory flaking rolls at a constant feed rate and at1,800 pounds gage pressure on the rolls, significant improvement wasapparent in the viscosity over extended operating times.

Such a result can be attributed to the heating of-the rolls which inturn caused better contact between rolls and to an easier disruption ofthe split at higher temperature. Actual physical measurements of the nipwidth became difficult in the less than 0.00l-inch range. However, whenrolls were kept from contact at 50 microns, or 0.002 inches, significantviscosity improvements were not obtained indicating that squeezing belowthe 50 microns was necessary. Many experimental runs have shown thatsqueezing of the split to less than 25 microns will give viscositieswhich are twice the viscosities obtained with particle thicknessesgreater than 25 microns. This phenomenon will be further illustrated bythe examples.

Other methods of reducing the splits to the particle thickness may bethrough extrusion with a screw extruder wherein the screw passes withinless than 25 microns of the extruder wall. Likewise, squeezing of thesplits between plates may also produce the desired results. The feedmaterial may be squeezed by forcing the split through a slit having aheight of less than 25 microns. However, flaking rolls were mostconveniently used. Chrome-plated steel or stainless steel rolls weremost satisfactory. Other methods of obtaining such squeezing action onthe splits will be apparent to those skilled in the art.

When practicing a preferred embodiment of this invention a suitable flowsheet'would be as follows.

ENDOSPERM SPLITS l i-- WATER TEMPERING DRYING GRINDING PRODUCT Theendosperm splits would be tempered in water to the preferred moisturecontent of 4362 percent. The tempered, softened splits would be fed tothe squeezing forces, preferably flaking rolls and squeezed to athickness less than 25 microns. The squeezed splits would then be driedand collected as product. Optionally, the squeezed splits could beground to various mesh sizes and dried. The grinding and drying could bedone simultaneously. lf grinding was used, it may be desirable toclassify the ground, squeezed, split flakes according to particle sizesince finely ground produce may be more desirable for certainapplications.

For convenience of operating in the laboratory, laboratory sizedequipment was used. The small scale equipment consisted of:

l. A 1-inch diameter variable screw feeder capable of feed rates of -400grams per minute feeding to;

2. a small laboratory flaker fitted with a hydraulic system to controlroll pressure and insure contact in the nip of the rolls and a set ofsprockets and gears for speed variations of the rolls, and a set of twoknives on each roll to remove the flakes and clean the rolls;

. two heat guns used to dry the flakes and capable of temperatures of upto 750 F. which were mounted in a tubular connection between the bottomof the flaker and a conveyor drier;

4. a section of electric conduit 1 /2 inches in diameter byapproximately 223 feet long which was insulated and connected in sixoblong loops to serve as a conveyor drier;

S. a small collection cyclone (6 inches in diameter X 2.5 inches indiameter X 24 inches long) connected to the drier and discharging into awidemouth collection bottle; and

6. an industrial vacuum cleaner connected to the cyclone to provide ameans of conveying the flakes through the drier and the cyclone.

The drier and flaker were fitted with thermometers at various points andthe whole of the other equipment was made to be as reproducible andcontrollable as possible. Total time, feeder exit to collection bottle,was approximately l2 seconds.

Flakes were preferably dried to less than percent moisture in order toprevent spoilage.

Of primary importance was the laboratory flaker which conp.s.i.

Flaking runs were made at various pressures. Since the pressure is avariable for determining flaked particle thickness it was found that aminimum of about 1,200 pounds pressure (gage) was needed on thelaboratory flaker and pressures as high as 2,000 pounds could beobtained on the laboratory equipment. However, minimum pressure willvary with the type of equipment, i.e. hydraulic cylinders, roll width,roll diameter, etc. it was found that flaked product viscosity,especially 2-minute viscosity increases with flaking pressure, while allelse is constant within acceptable limits. Where possible, the nip widthbetween the rolls was measured, but when operating in the area of0.00l-inch width, physical measuring means, i.e. feeler gages and shimstock, became impossible. Therefore, flake thickness or parting of therolls was determined by calculation at a feed rate of 1 gram moisturefree basis (M.F.B.)/roll revolution. it is known that 1 gram of splitson a moisture free basis will weight approximately 1.93 grams at 48percent moisture. The density of the endosperm split is approximately1.5, of water I and thus at 48 percent moisture content the density ofthe split will be approximately 1.26. Therefore, a 1 gram M.F.B. ofendosperm splits will occupy 1.5 3 cm. at 48 percent moisture. Using thelaboratory flaker at a feed rate of 1 gram M.F.B./roll revolution overthe effective flaking area of 8.9 centimeters (flaking width in cm.) by46 centimeters (roll circumference in cm.) the flake thickness of 48percent moisture flakes would be 37 microns at a roll pressuresufficient to squeeze splits as thin as possible, in this case, about1,800 pounds. Using this as the basis, various feed rates were run onthe flaker resulting in various flake thicknesses. The results aresummarized in the examples. When operating the flaker, the dry flakerproduct was removed from the cyclone and broken so as to pass an S-meshscreen. Flake viscosity was determined by using a blender motor and aVariac, a 500 milliliter blender jar and cover, and a BrookfieldViscometer. To determine viscosity, 5 grams dry weight of gum were addedto 495 milliliters of distilled water at 25 C. The procedure was toplace 250 cc. of water in the jar and set the Variac at 20-30 volts. Thegum was added and mixed in the blender for 10 seconds. The remainder ofthe water was added to the stopped blender. The cover was placed on theblender and at 30 seconds the blender was turned on and set at maximumspeed and allowed to mix for 1 minute. Using the Brookfield Viscometerwith a No. 4 spindle at 20 r.p.m. the viscosity was read at exactly 2minutes and again at 2 hours. The results are summarized in theexamples.

When using other methods and other equipment to squeeze guar splits toless than 25 microns, optimum operating conditions are easily obtainablethrough these simple laboratory testing techniques. Methods of obtainingoptimum conditions on other equipment will be readily apparent to thoseskilled in the art.

The squeezed splits or dry flakes when processed according to theteachings of this invention produce a product with superior viscosityproducing properties and eliminates the requirement of subsequentgrinding. The coarse products produced by the process of this inventionare readily water dispersible. This behavior essentially eliminates thetendency for the formation of lumps in the aqueous sols. The squeezedendosperm or dry flakes may be dispersed directly in water in certainapplications; however, the processed flakes may be reduced to a coarsesize range, such as primarily between 30 and mesh, and 40 and 200 mesh.The flakes may be further reduced to a finely divided condition, such asall 200 mesh and all 325 mesh for various other applications. Flakesground to finer mesh sizes do tend to produce slightly higherviscosities, i.e. up to 10 percent greater than the same product leftcoarsely sized, i.e. larger than about mesh.

The following examples will further illustrate but are not intended tolimit the scope of this invention.

EXAMPLE I Endosperm splits were prepared as disclosed in assignees US.Pat. No. 3,132,681, by Keen. The splits were tempered to an equilibriummoisture content of 48.5-51 percent over approximately a 1 hour period.The tempered splits were fed to the laboratory flaker as describedabove. Viscosities were determined as indicated above. The results andoperating con- EXAMPLE IV A further desirable characteristic of theproduct of this invention is the rapid rate of hydration in cold water.En-

ditions are summarized in table I. 5 dosperm splits were prepared as inexample 1. The splits were TABLE I Feed moisture Flake content Roll 2minute 2 hour Feed rate, grams thickness, percent pressure, viscosity,viscosity, M.F.B./roll rev. microns water lbs. gauge cps. cps.

1.05 38. 48 48. 5 1, 800 2,150 0.65 24. 05 51. 1, 800 2, 800 7, 950 0.4817. 76 48. 0 l, 800 4, 550 7, 750 0.47 17. 30 48. 0 1,800 4,600 7, 9000.44 16. 28 48. 0 l, 800 4, 650 7, 800 0.42 15. 24 4s. 0 1, 800 5, 250s, 400 0.25 9. 25 48. 5 1,800 5,600 a, 300

tem ered to an e uilibrium moisture content of 50 ercent EXAMPLE 11 p qp over approximately 1 hour. The laboratory flaker was set to flake to aparticle thickness of 10,11. and 19 1 respectively. The roll pressurewas 1,800 lbs. per square inch, gage at 1 10 roll r.p.m. and a rolltemperature of about 140 F. The flakes were dried and ground in animpact mill and sifted into fractions of a mesh size as indicated below.Controls were run on a commercially available guar gum and on alaboratory flaked material having a particle thickness of 32 1.Viscosities for each sample were determined as indicated above.

TABLE II Feed moisture Flake Roll Roll content Roll 2 minute 2 hour Feedrate, grams thickness, speed, temp., percent pressure, viscosity,viscolity, M.F.B./roll rev. microns r.p.m. water lbs. gauge cps. cps.

0.73 22. 6 160 140 56 1, 800 3, 000 7, 300 0.56 16. 2 160 140 56 1, 8005,200 7, 650 0.28 8. 1 100 140 56 1, 800 5, 200 s, 050 0.91- 25. 0 160140 01 1,800 4, 400 7, 950 0.48. 13. 0 160 140 61 1,800 5, 900 8,0000.27 7. 9 100 140 61 1, 300 6, 250 s, 150 0.59. 17. 1 160 140 60 1,8005,000 8,000 0.35 10. 2 160 140 66 1,800 5, 400 s, 150

EXAMPLE m TABLE IV In practicing a further embodiment of this inventionthe flakes were ground to coarse and fine particles and the viscosi- IPercent ty at various mesh sizes determined. By grinding the flakes, itggfig ag N 1 9 213; was determined that the Viscosities obtained wereslightly so fraction 2min. 2 hr. hr.) 100 higher with the finely groundparticles than with the coarse ground particles. The splits wereprepared and flaked as in cX- Sample A: ample l with a split moisturecontent of 49 percent and a flakf gfffgh gg g 100 850 5 950 14 mg rollrevolution of 96 r.p.m., a flaking pressure of 1,800 Fraction: h 31 350400 5 5 pounds and a feed rate of 0.47 grams per roll of revolution.jfig bjgg fi :2 850 2: The flake thickness was determined to be 17.39micron 150+200 4. 2 1,800 5,300 34 0 8.1 3,250 5, 000 65 Viscositieswere determined as in example i. The results are siftingloss 1,0summarized in the table below. Original flakes B, were Samp 131 10pflake thickness mesh processed in a similar manner except the feed ratewas 0.34 mum B813 100 5,300 ,200 70 g m per r ll of r lu ion. 1 1 15 2.70 8 31 1 w g -1oo+156 IIIIII 1 p 11 13 8 81 15 e; -150 200 8 7 TABLE IIIT 34. a e, 350 s, 150 78 silitirg loss 0 Sam 0 Flake vlscoslty l rrflake thickness mesh Product Thickness n) fraction s is 100 5,450 8,50064 in microns Ground 100 5, 350 8,250 65 2 minute 2 o 0 31.3 4,950 3,250 59 i3"? i383 3' 128 8?. Original flakes A (no mil1ing) 17. 30 5, 6758, 900 :gg I 2 4 3: 400 550 77 55 flakes finely ground fg 2. s

ikro-Samplmill as s... 17. 39 5,900 8,550 sample Original flakes B (nomillin l2. 5 5, 950 8, 700 fl k thickness h Fraction B recovered betweenfraction as is 00 2 450 7 500 33 mesh (65% yield) l2. 5 5, 400 8,200Groun 0 00 1I 800 6, 00 2 Fraction B recovered below 33 6 00 7, 0 9 5 Y5 9.450 0+150 24. 9 1,750 7,000 25 flakes finely -+200 as 3,200 7,100 45h ikro Samplmill high speed 12. 5 6, 050 8, 600 o0 2 4' 550 6, 350 66 75Sitting loss 4. 5

The commercial sample and the laboratory sample of 32p. flake thicknesswere similar and did not dissolve and hydrate at either the high rate orto the same high viscosity as material flaked to less than 18-20 micronsthickness.

Further benefits are derived from the product of this invention in thatcoarse particles squeezed to less than 25 micron thickness formconsiderably fewer gu mballs and livers in aqueous sols while hydratingto provide the same viscosity as finely ground gums. A gumball isdefined as a lump of gum which has a dry center. A liver" is defined asa lump of gum which has a wet center. Gumballs and livers are highlyundesirable since smooth aqueous sols are required in many commercialapplications, e.g. drilling mud, food stuffs, etc. Gumballs arecharacteristically formed by dispersion of finely ground gums.

By squeezing or flaking the splits to a thickness of less than V 25microns many processing and product advantages are obtained. In additionto the unexpected increase in viscosity as well as the possible rapidhydration without gumballs, a broad range of mesh sizes and hydrationrates within each mesh may be chosen. The process of flaking asdescribed herein will produce the desired results in all of the gumproducts, i.e. derivatives of guar gum such as hydroxypropyl guar,locust bean gum products, etc. Likewise, unexpected advantages areobtained from subsequent grinding such as higher viscosities obtainedfrom finely ground products. The coarser products produced from thesplits will also flow well with good hydration. Other advantages fromthe processing of splits by squeezing in a flaker or other equipment toa thickness of less than 25 microns will be readily apparent to thoseskilled in the art.

Iclaim:

1. A process for the production of mucilaginous material from leguminousseeds, the endosperm sections of which contain galactomannans comprisedof tempering said endosperm sections to a moisture content of 3070percent by-weight of water and squeezing said endosperm sections in saidmoistened condition to a thickness of less than 25 microns.

2. A process as in claim 1 wherein said endosperm sections are squeezedto a thickness of less than 25 microns by passing said endospermsections between rolls.

3. A process as in claim 2 wherein said rolls are heated to to 200 F.

4. A process as in claim 2 wherein said rolls are kept under sufficientpressure to keep the nip width between the rolls at less than 25 micronswhen passing said endosperm sections between said rolls.

5. A process as in claim I wherein said moistened endosperm sections aresqueezed to less than 20 microns.

6. A process according to claim 1 wherein said squeezed endospermsections are dried and ground.

7. A process according to claim 1 wherein said squeezed endospermsections are dried to a moisture content of less than 1 5 percent byweight of water.

8. A process as in claim 1 wherein said squeezed endosperm sections areground to less than about mesh.

9. A process as in claim I wherein said squeezed endosperm sections areground to greater than about 150 mesh.

10 A process as in claim 1 wherein said moistened endosperm sections aresqueezed to less than 15 microns.

11. A process as in claim 1 wherein said endosperm sections are temperedto a moisture content of 4362 percent by weight of water.

12. A leguminous seed containing galactomannans comprised of endospermsections squeezed to a thickness of less than 25 microns.

